1. How do atoms change???? IONS & ISOTOPES

2. IONS 1.In a neutral atom, the # of protons = # of electrons (because the signs balance each other out). 2.Atoms are reactive because they want to fill their outermost energy shells. 3.Therefore, atoms gain and lose electrons to become stable (full outer shells).

3. 4.Atoms that gain electrons become negative ions called “anions”. 5.Atoms that lose electrons become positive ions called “cations”. 6.Metals form positive ions (cations). 7.Nonmetals form negative ions (anions).

4. Group1 (1A) 2 (2A) 13 (3A) 14 (4A) 15 (5A) 16 (6A) 17 (7A) 18 (8A) Valence Electrons 12345678 Ion Formed +1+2+3 +/- 4-3-2 None ***Carbon doesn’t really form ions. Prefers to make a covalent bond.

5. Transition metals can form multiple ions because they have so many electrons.

6. ISOTOPES 1.Are when atoms have the same # of protons (and electrons) but different number of neutrons. 2.why the atomic mass is called an “average”. It is a combination of all the isotopes that exist for that particular element.

7. 3.Remember…changing the neutron number of an atom ONLY affects the MASS. 4.Many elements do not have alternate forms. 5.Isotopes that are too heavy are said to be “unstable”. These are useful because they are radioactive. 6.Carbon dating- using the isotopes of carbon to examine how old organic matter is.